Step 1: Concept Overview:
The question requires identifying the mineral element essential for the enzyme involved in biological nitrogen fixation.
Step 2: Detailed Analysis:
Biological nitrogen fixation, the conversion of \(N_2\) into \(NH_3\), is facilitated by the nitrogenase enzyme complex.
Nitrogenase, a metalloenzyme, relies on metal ions as cofactors for its activity. The prevalent form of nitrogenase comprises two crucial metallic components:
An iron (Fe) protein.
An iron-molybdenum (Fe-Mo) protein.
The active site, where nitrogen binds and is reduced, features the Iron-Molybdenum cofactor (FeMoco), a complex metal cluster. Consequently, Molybdenum (Mo) is a vital micronutrient for organisms that fix nitrogen. Iron (Fe) is also crucial.
While Zinc, Copper, and Manganese are also important micronutrients for plants, they are not key components of the nitrogenase active site.
Step 3: Conclusion:
Molybdenum is essential for nitrogen fixation as it is a component of the nitrogenase enzyme.